fix(cli-demo): interrupt Loader boot on signals

Race Loader startup with the process abort signal so SIGINT and SIGTERM can settle the one-shot CLI even when initialization has not returned a Context.

If boot settles after cancellation, dispose the late context asynchronously instead of recreating the wait. Contain late boot rejection and report a late disposal failure on stderr.

Cover prompt interruption, late context disposal, late boot rejection, and cleanup failure with focused CLI regressions.

packages/examples/cli-demo/src/cli.ts

@@ -294,6 +294,53 @@ function renderResult(outputFormat: OutputFormat, result: CliResult): string {
   return outputFormat === 'text' ? `${result.result}\n` : `${JSON.stringify(result)}\n`
 }
 
+/**
+ * Race Loader boot with cancellation without abandoning a context that becomes
+ * available after the caller has been released. Waiting for that late context
+ * would recreate the signal hang, so its disposal and diagnostics run detached.
+ */
+async function bootInterruptibly(
+  start: () => Promise<Context>,
+  signal: AbortSignal | undefined,
+  disposeLateContext: (ctx: Context) => Promise<void>,
+  reportLateDisposalFailure: (error: unknown) => void,
+): Promise<Context> {
+  if (signal === undefined) return await start()
+  if (signal.aborted) throw new CliInterruptedError(interruptionReason(signal))
+
+  let onAbort!: () => void
+  const interruptedBoot = new Promise<never>((_resolve, reject) => {
+    onAbort = (): void => {
+      reject(new CliInterruptedError(interruptionReason(signal)))
+    }
+    signal.addEventListener('abort', onAbort, { once: true })
+    /* v8 ignore next -- closes registration against a non-standard synchronously mutating signal */
+    if (signal.aborted) onAbort()
+  })
+  const booting = Promise.resolve().then(start)
+  try {
+    return await Promise.race([booting, interruptedBoot])
+  } catch (error: unknown) {
+    // The awaited race permits the signal to change after the preflight check.
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    if (signal.aborted) {
+      void booting.then(
+        async (lateContext) => {
+          try {
+            await disposeLateContext(lateContext)
+          } catch (error: unknown) {
+            reportLateDisposalFailure(error)
+          }
+        },
+        () => {},
+      )
+    }
+    throw error
+  } finally {
+    signal.removeEventListener('abort', onAbort)
+  }
+}
+
 /**
  * Render a non-completed turn reason for stderr.
  * @param reason - durable turn ending to describe.
@@ -349,8 +396,12 @@ export async function executeCli(args: readonly string[], runtime: CliRuntime =
   let diagnostic: string | undefined
   try {
     loadEnvironment(CLI_NAME, cwd, line => writeStderr(line))
-    ctx = await bootContext(CLI_NAME, resolveConfigPath(command.configPath, undefined, cwd))
-    if (runtime.signal?.aborted === true) throw new CliInterruptedError(interruptionReason(runtime.signal))
+    ctx = await bootInterruptibly(
+      () => bootContext(CLI_NAME, resolveConfigPath(command.configPath, undefined, cwd)),
+      runtime.signal,
+      disposeContext,
+      error => writeStderr(`${CLI_NAME}: dispose after interrupted boot failed: ${toError(error).message}\n`),
+    )
     const result = await runOneShot(ctx, {
       task: command.task,
       ...runtime.signal === undefined ? {} : { signal: runtime.signal },

packages/examples/cli-demo/tests/cli.spec.ts

@@ -199,6 +199,83 @@ describe('runOneShot and executeCli', () => {
     expect(stderr).toContain('boot exploded')
   })
 
+  it('interrupts Loader boot and contains every late boot outcome', async () => {
+    const abort = new AbortController()
+    const lateContext = new Context()
+    liveContexts.push(lateContext)
+    const boot = Promise.withResolvers<Context>()
+    const disposed = Promise.withResolvers<undefined>()
+    let disposeCalls = 0
+    let stderr = ''
+    const running = executeCli(['task'], {
+      signal: abort.signal,
+      boot: () => boot.promise,
+      loadEnv: () => {},
+      writeStdout: () => {},
+      writeStderr: (chunk) => { stderr += chunk },
+      dispose: async (ctx) => {
+        disposeCalls += 1
+        await ctx.fiber.dispose()
+        disposed.resolve(undefined)
+      },
+    })
+    abort.abort('received SIGTERM')
+    await expect(running).resolves.toBe(1)
+    expect(stderr).toContain('received SIGTERM')
+    expect(disposeCalls).toBe(0)
+    boot.resolve(lateContext)
+    await disposed.promise
+    expect(disposeCalls).toBe(1)
+
+    const rejectedBoot = Promise.withResolvers<Context>()
+    const rejectedAbort = new AbortController()
+    const rejected = executeCli(['task'], {
+      signal: rejectedAbort.signal,
+      boot: () => rejectedBoot.promise,
+      loadEnv: () => {},
+      writeStdout: () => {},
+      writeStderr: () => {},
+    })
+    rejectedAbort.abort('stop rejected boot')
+    await expect(rejected).resolves.toBe(1)
+    rejectedBoot.reject(new Error('late boot rejection'))
+    await Promise.resolve()
+
+    let ordinaryBootStderr = ''
+    const ordinaryBootFailure = await executeCli(['task'], {
+      signal: new AbortController().signal,
+      boot: async () => { throw new Error('ordinary boot failure') },
+      loadEnv: () => {},
+      writeStdout: () => {},
+      writeStderr: (chunk) => { ordinaryBootStderr += chunk },
+    })
+    expect(ordinaryBootFailure).toBe(1)
+    expect(ordinaryBootStderr).toContain('ordinary boot failure')
+
+    const failedCleanupBoot = Promise.withResolvers<Context>()
+    const failedCleanupAbort = new AbortController()
+    const cleanupFailure = Promise.withResolvers<undefined>()
+    const failedCleanupContext = new Context()
+    liveContexts.push(failedCleanupContext)
+    const failedCleanup = executeCli(['task'], {
+      signal: failedCleanupAbort.signal,
+      boot: () => failedCleanupBoot.promise,
+      loadEnv: () => {},
+      writeStdout: () => {},
+      writeStderr: (chunk) => {
+        if (chunk.includes('dispose after interrupted boot failed: late cleanup')) cleanupFailure.resolve(undefined)
+      },
+      dispose: async (ctx) => {
+        await ctx.fiber.dispose()
+        throw new Error('late cleanup')
+      },
+    })
+    failedCleanupAbort.abort('stop failed cleanup boot')
+    await expect(failedCleanup).resolves.toBe(1)
+    failedCleanupBoot.resolve(failedCleanupContext)
+    await cleanupFailure.promise
+  })
+
   it('renders text, flushes a persisted fresh session, and disposes the context', async () => {
     const { ctx, agent, persistenceRoot } = await harness([textResponse('final answer')])
     const output = await invoke(ctx, ['task'])